x86: restore old GART alloc_coherent behavior (1d990882) · Commits · 戴 / test

Currently, GART alloc_coherent tries to allocate pages with GFP_DMA32 for a device having dma_masks > 24bit < 32bits. If GART gets an address that a device can't access to, GART try to map the address to a virtual I/O address that the device can access to. But Andi pointed out, "The GART is somewhere in the 4GB range so you cannot use it to map anything < 4GB. Also GART is pretty small." http://lkml.org/lkml/2008/9/12/43 That is, it's possible that GART doesn't have virtual I/O address space that a device can access to. The above behavior doesn't work for a device having dma_masks > 24bit < 32bits. This patch restores old GART alloc_coherent behavior (before the alloc_coherent rewrite). Signed-off-by:

FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp> Signed-off-by:

Ingo Molnar <mingo@elte.hu>

arch/x86/kernel/pci-gart_64.c

+20 −23

Original line number	Diff line number	Diff line
		@@ -487,31 +487,28 @@ static void *
		gart_alloc_coherent(struct device dev, size_t size, dma_addr_t dma_addr,
		gfp_t flag)
		{
		void *vaddr;
		dma_addr_t paddr;
		unsigned long align_mask;
		u64 dma_mask = dma_alloc_coherent_mask(dev, flag);
		struct page *page;

		vaddr = (void *)__get_free_pages(flag \| __GFP_ZERO, get_order(size));
		if (!vaddr)
		if (force_iommu && !(flag & GFP_DMA)) {
		flag &= ~(__GFP_DMA \| __GFP_HIGHMEM \| __GFP_DMA32);
		page = alloc_pages(flag \| __GFP_ZERO, get_order(size));
		if (!page)
		return NULL;

		paddr = virt_to_phys(vaddr);
		if (is_buffer_dma_capable(dma_mask, paddr, size)) {
		*dma_addr = paddr;
		return vaddr;
		}

		align_mask = (1UL << get_order(size)) - 1;
		paddr = dma_map_area(dev, page_to_phys(page), size,
		DMA_BIDIRECTIONAL, align_mask);

		*dma_addr = dma_map_area(dev, paddr, size, DMA_BIDIRECTIONAL,
		align_mask);
		flush_gart();

		if (*dma_addr != bad_dma_address)
		return vaddr;

		free_pages((unsigned long)vaddr, get_order(size));
		if (paddr != bad_dma_address) {
		*dma_addr = paddr;
		return page_address(page);
		}
		__free_pages(page, get_order(size));
		} else
		return dma_generic_alloc_coherent(dev, size, dma_addr, flag);

		return NULL;
		}

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